To the Editor:—
Since Cloward's article1 on cervical diskography appeared, this procedure seems to have been the object of great controversy. When Holt's evaluation of the procedure2 was published, many reputable surgeons developed serious doubts as to the validity of this test. Later published opinions of diskography3 seem to be gradually becoming more favorable.The author recently listened to a discussion of diskography in which one physician stated that all diskograms could be made positive if enough pressure were applied, just as retrograde pyelography could be similarly distorted. It seemed to me that a simple application of scientific method to this, namely, trying to control the variables, would establish the true value of the test.
Several neurosurgeons were tested while using a syringe attached to a pressure gauge. The variation between the maximum injection pressure used by different neurosurgeons was from 19 to 52 pounds per